scholarly journals Vibrational Properties of CO Adsorbed on Au Single Atom Catalysts on TiO2(101), ZrO2(101), CeO2(111), and LaFeO3(001) Surfaces: A DFT Study

2021 ◽  
Author(s):  
Ho Viet Thang ◽  
Farahnaz Maleki ◽  
Sergio Tosoni ◽  
Gianfranco Pacchioni
Keyword(s):  
Experimental Study ◽  
Comparative Study ◽  
Local Environment ◽  
Blue Shift ◽  
Single Atom ◽  
Vibrational Properties ◽  
Single Atoms ◽  
Correct Reproduction ◽  
Molecular Compounds ◽  
Positively Charged

AbstractThe nature and local environment of Au single atoms supported and stabilized on four different oxides is studied by means of DFT + U calculations using CO as probe molecule and its stretching frequency, ωe, as a fingerprint of the site where the Au atom is bound. Four oxides are considered, anatase TiO2, tetragonal ZrO2, cubic CeO2, and a perovskite LaFeO3. In this latter case a recently reported experimental study has detected a stretching mode for CO adsorbed on Au1/LaFeO3 of 2215 cm−1, with a large blue shift, ∆ω(CO) = 72 cm−1 with respect to free CO. In order to identify the Au adsorption site that can give rise to this large blue-shift we have considered five cases: (a) Au replacing a lattice cation, (Au)subM; (b) Au replacing a lattice O anion, (Au)subO; (c) Au adsorbed on the surface, (Au)ads; (d) Au bound to an extra O atom on the surface, (AuO)ads, or (e) Au bound to two extra O atoms on the surface, (AuO2)ads. It turns out that the correct reproduction of ∆ω for CO adsorbed on positively charged gold, Auδ+, is challenging for DFT. Therefore, we have performed a comparative study of Auδ+-CO molecular compounds for which ωe(CO) is known experimentally using various kinds of DFT functionals and accurate CCSD and CCSD(T) quantum chemistry methods. Also based on this comparison we propose a tentative assignment for the observed frequency of CO adsorbed on Au1/LaFeO3 single atom catalyst. Graphic Abstract

Tunable Carbon Surface from Mono- to Multi-Metallic Single Atoms

2020 ◽  
Author(s):  
Weihong Lai ◽  
Heng Wang ◽  
Quan jiang ◽  
Zichao Yan ◽  
Hanwen Liu ◽  
...  
Keyword(s):  
Synergistic Effects ◽  
Structural Evolution ◽  
Charge Compensation ◽  
Catalytic Reactions ◽  
Single Atom ◽  
Carbon Surface ◽  
Hydrogen Electrode ◽  
Single Atoms ◽  
Mass Activity ◽  
Co Doped

<p>Herein, we develop a non-selective charge compensation strategy to prepare multi-single-atom doped carbon (MSAC) in which a sodium p-toluenesulfonate (PTS-Na) doped polypyrrole (S-PPy) polymer is designed to anchor discretionary mixtures of multiple metal cations, including iron (Fe<sup>3+</sup>), cobalt (Co<sup>3+</sup>), ruthenium (Ru<sup>3+</sup>), palladium (Pd<sup>2+</sup>), indium (In<sup>3+</sup>), iridium (Ir<sup>2+</sup>), and platinum (Pt<sup>2+</sup>) . As illustrated in Figure 1, the carbon surface can be tuned with different level of compositional complexities, including unary Pt<sub>1</sub>@NC, binary (MSAC-2, (PtFe)<sub>1</sub>@NC), ternary (MSAC-3, (PtFeIr)<sub>1</sub>@NC), quaternary (MSAC-4, (PtFeIrRu)<sub>1</sub>@NC), quinary (MSAC-5, (PtFeIrRuCo)<sub>1</sub>@NC), senary (MSAC-6, (PtFeIrRuCoPd)<sub>1</sub>@NC), and septenary (MSAC-7, (PtFeIrRuCoPdIn)<sub>1</sub>@NC) samples. The structural evolution of carbon surface dictates the activities of both ORR and HER. The senary MSAC-6 achieves the ORR mass activity of 18.1 A·mg<sub>metal</sub><sup>-1</sup> at 0.9 V (Vs reversible hydrogen electrode (RHE)) over 30K cycles, which is 164 times higher than that of commercial Pt/C. The quaternary MSAC-4 presented a comparable HER catalytic capability with that of Pt/C. These results indicate that the highly complexed carbon surface can enhance its ability over general electrochemical catalytic reactions. The mechanisms regarding of the ORR and HER activities of the alternated carbon surface are also theoretically and experimentally investigated in this work, showing that the synergistic effects amongst the co-doped atoms can activate or inactivate certain single-atom sites.</p>

Improving peroxymonosulfate activation by copper ion-saturated adsorbent-based single atom catalysts for the degradation of organic contaminants: electron-transfer mechanism and the key role of Cu single atoms

2021 ◽  
Author(s):  
Jingwen Pan ◽  
Baoyu Gao ◽  
Pijun Duan ◽  
Kangying Guo ◽  
Muhammad Akram ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Organic Contaminants ◽  
High Salinity ◽  
Copper Ion ◽  
Single Atom ◽  
Electron Transfer Mechanism ◽  
Persulfate Oxidation ◽  
Single Atoms ◽  
Oxidation Technology

Nonradical pathway-based persulfate oxidation technology is considered to be a promising method for high-salinity organic wastewater treatment.

Tailoring the Local Environment of Platinum in Single‐Atom Pt1/CeO2 Catalysts for Robust Low‐Temperature CO Oxidation

2021 ◽  
Author(s):  
Dong Jiang ◽  
Yonggang Yao ◽  
Tangyuan Li ◽  
Gang Wan ◽  
Xavier Isidro Pereira-Hernández ◽  
...  
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Local Environment ◽  
Single Atom ◽  
Low Temperature Co Oxidation

Comparative Study of the Reconstruction of Articular Cartilage Defects with Free Costal Perichondrial Grafts and Free Tibial Periosteal Grafts: An Experimental Study on Rabbits

1999 ◽  
Vol 65 (5) ◽  
pp. 402-407 ◽  
Author(s):  
A. Carranza-Bencano ◽  
M. Perez-Tinao ◽  
P. Ballesteros-Vazquez ◽  
J. R. Armas-Padron ◽  
A. Hevia-Alonso ◽  
...  
Keyword(s):  
Experimental Study ◽  
Articular Cartilage ◽  
Comparative Study ◽  
Cartilage Defects ◽  
Articular Cartilage Defects

scholarly journals Comparative study of single-atom gold and iridium on CeO2{111}

2021 ◽  
Vol 154 (16) ◽  
pp. 164703
Author(s):  
Cameron J. Owen ◽  
Stephen J. Jenkins
Keyword(s):  
Comparative Study ◽  
Single Atom

Synergy of Single Atoms Pd and Oxygen Vacancies on In2O3 for Highly Selective C1 Oxygenates Production from Methane under Visible Light

2021 ◽  
Author(s):  
Lei Luo ◽  
Lei Fu ◽  
Huifen Liu ◽  
Youxun Xu ◽  
Jialiang Xing ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Single Atom ◽  
Electron Transfer Pathway ◽  
Mild Conditions ◽  
Single Atoms ◽  
Primary Products ◽  
Critical Issues ◽  
Regulation Of Activity ◽  
Visible Irradiation ◽  
Dft Modelling

Abstract Methane (CH4) oxidation to high value chemicals under mild conditions through photocatalysis is a sustainable and appealing pathway, nevertheless confronting the critical issues on both conversion and selectivity. Herein, under visible irradiation (420 nm), the synergy of palladium (Pd) atom cocatalyst and oxygen vacancies (OVs) on In2O3 nanorods enabled superior photocatalytic CH4 activation by O2. The optimised catalyst reached ca. 100 µmol·h− 1 of C1 oxygenates, with a selectivity of primary products (CH3OH and CH3OOH) up to 82.5 %. Mechanism investigation elucidated that such superior photocatalysis was induced by the dedicated function of Pd single atoms and oxygen vacancies on boosting hole and electron transfer pathway, respectively. O2 was proven to be the only oxygen source for CH3OH production, while H2O acted as the promoter for efficient CH4 activation through ·OH production and facilitated product desorption as indicated by DFT modelling. This work thus provides new understandings on simultaneous regulation of activity and selectivity by the significant synergy of single atom cocatalysts and oxygen vacancies.

scholarly journals Interfacial-confined coordination to single-atom nanotherapeutics

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Limei Qin ◽  
Jie Gan ◽  
Dechao Niu ◽  
Yueqiang Cao ◽  
Xuezhi Duan ◽  
...  
Keyword(s):  
Therapeutic Strategy ◽  
Single Atom ◽  
Oxygen Species ◽  
High Quality ◽  
Efficient Energy ◽  
Coordination Strategy ◽  
Single Atoms ◽  
Highly Active ◽  
Narrow Bandgap ◽  
Catalytic Sites

AbstractPursuing and developing effective methodologies to construct highly active catalytic sites to maximize the atomic and energy efficiency by material engineering are attractive. Relative to the tremendous researches of carbon-based single atom systems, the construction of bio-applicable single atom materials is still in its infancy. Herein, we propose a facile and general interfacial-confined coordination strategy to construct high-quality single-atom nanotherapeutic agent with Fe single atoms being anchored on defective carbon dots confined in a biocompatible mesoporous silica nanoreactor. Furthermore, the efficient energy conversion capability of silica-based Fe single atoms system has been demonstrated on the basis of the exogenous physical photo irradiation and endogenous biochemical reactive oxygen species stimulus in the confined mesoporous network. More importantly, the highest photothermal conversion efficiency with the mechanism of increased electron density and narrow bandgap of this single atom structure in defective carbon was proposed by the theoretical DFT calculations. The present methodology provides a scientific paradigm to design and develop versatile single atom nanotherapeutics with adjustable metal components and tune the corresponding reactions for safe and efficient tumor therapeutic strategy.

Photoinduced Synergistic Catalysis on Zn Single-Atom-Loaded Hierarchical Porous Carbon for Highly Efficient CO2 Cycloaddition Conversion

2021 ◽  
Author(s):  
Lin Gong ◽  
Ji Sun ◽  
Yousong Liu ◽  
Guangcheng Yang
Keyword(s):  
Solar Energy ◽  
Porous Carbon ◽  
Single Atom ◽  
Hierarchical Porous Carbon ◽  
Reaction Conditions ◽  
Synergistic Catalysis ◽  
Single Atoms ◽  
Significant Challenge ◽  
Highly Efficient ◽  
Hierarchical Porous

The use of solar energy to drive efficient CO2 cycloaddition conversion under mild reaction conditions is highly desired but remains a significant challenge. In this communication, a Zn single-atoms-loaded N-doped...

N2 positively charged defects in diamond. A quantum mechanical investigation of the structural, electronic, EPR and vibrational properties

2020 ◽  
Vol 8 (15) ◽  
pp. 5239-5247 ◽  
Author(s):  
Giulio Di Palma ◽  
Francesco Silvio Gentile ◽  
Valentina Lacivita ◽  
William C. Mackrodt ◽  
Mauro Causà ◽  
...  
Keyword(s):  
Ab Initio ◽  
Quantum Mechanical ◽  
Vibrational Properties ◽  
Quantum Mechanical Calculations ◽  
Mechanical Investigation ◽  
Crystal Code ◽  
Charged Defects ◽  
Positively Charged ◽  
Vibrational Characterization

Structural, EPR and vibrational characterization of the N2, N+2 and N++2 defects in diamond from ab initio quantum-mechanical calculations with the CRYSTAL code.

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